1. Field of the Invention
This invention relates to spark ignition of internal combustion engines having multiple cylinders such as multi-cylinder, reciprocating piston engines and multi-chambered rotary engines.
2. Description of the Prior Art
Internal combustion engines of multiple combustion chambers most commonly employ a Kettering ignition system to generate a train of high voltage surges useful for spark ignition. This system utilizes an ignition coil having primary and secondary windings to generate a train of high voltage surges in the coil's secondary windings by the intermittent building and collapsing of the magnetic field generated by a low voltage, pulsed current flow through the primary windings of the coil. The train of high voltage pulses so generated is applied through a distributor means including a rotor and cooperative terminal posts to direct a high voltage pulse to the proper cylinder for ignition of the air-fuel mixture in the cylinder at a predetermined, timed angular relationship to the position of the piston in the cylinder in a reciprocating piston engine or the position of the rotor in the toroidal chamber of a rotary engine. Typically, with a reciprocating engine, the voltage pulse is applied at an angle from zero to about 45.degree. before the piston reaches its top dead center position.
The train of voltage pulses of low voltage applied to the primary windings of the ignition coil is generally applied from the battery of the engine with breaker points which are actuated by a cam mounted on the distributor shaft to open and close the circuit at the preselected, proper times for building and collapsing the magnetic field in the ignition coil, thereby generating the train of high voltage pulses employed for ignition.
Optimum performance of an engine demands a variation in ignition timing which is responsive to either or both of engine speed or load. To this end, suitable spark advance means are provided whereby the ignition timing can be advanced in response to increasing speed or loading of the engine.
Commonly, the distributor and pulse generator contained within the distributor housing are driven by a mechanical linkage from the cam shaft of the engine. The cam shaft, in turn, is driven by mechanical gearing or chain linkage from the crankshaft of the engine. At high engine speeds, such as commonly encountered in racing engines, e.g., greater than about 5,000 revolutions per minute, the aforedescribed mechanical linkages between the pulse generator and the output shaft or crankshaft of the engine can cause a considerable error in the ignition timing, i.e., the timed angular relationship between such shaft and the pulses of the train of voltage pulses. This error is caused by an unavoidable lash in the mechanical gearing or chain linkage and/or the torsional strain on the cam shaft. This causes a loss in the amount of preset advance in the train of ignition voltage pulses, thereby resulting in a loss of power developed by the engine.
A great variety of ignition systems have been proposed to improve the basic Kettering system of spark ignition. Most of these systems, however, have employed pulse generating means which include a rotatable member that is driven through a complex mechanical linkage from the crankshaft and which thereby suffers the aforedescribed disadvantageous loss of power at high engine speeds. It is, therefore, an object of this invention to provide a voltage pulse generator which includes rotatable means mounted directly on the output shaft of the engine at a precise angular orientation thereto.
It is desirable in racers to have means whereby the ignition timing can be varied by the driver. In particular, it is desirable that provision be made for the variation in the amount of advance in the ignition timing cycle so that the engine can be readily started and operated throughout the range of engine speeds encountered in racing. It is also desirable that means is provided to vary the degree of advance of the ignition timing cycle in response to engine temperatures to avoid overheating the engine which can occur when operating an engine at maximum spark advance over prolonged periods of time, such as encountered in long distance races.